In various manufacturing operations a power source, such as an electric motor has a drive shaft which in turn drives an apparatus at a fixed speed. It will be understood that this speed could be changed by changing the speed of the motor, or by a speed changing gearbox or the like between the motor and the shaft. However, by way of a specific example, it is often desired to have the speed of the driven apparatus remain constant. Nevertheless, it may be desirable from time to time to have the phase of the driven apparatus differ from the phase of the driving motor (or the gearbox from the driving motor).